I see no actual prices posted by anyone, so here is something to use as a starting point:

Anywhere between $80,000 to $1 million. Realistically, around $160,000 to $650,000.

I am assuming that you don't have anything exclusive and that it is a run-of-the-mill (no offense meant!) web development shop.

Some factors that will push it to the higher end:

  - Great accounting and financial records
  - Steady clients
  - Large orders
  - Exclusivity (others can't do what you do)
  - Talented employees, if any, who will stay after sale

I posted this just so you have something to start with. You know your situation better than me or anyone else.